Study shows how flu virus keeps time

Researchers have found a potential weakness in the armor of the influenza virus, which is causing a tough flu season across the United States this year. They’ve found a flaw in a timekeeping mechanism that programs the virus to stay in the cells it infects.

This could eventually help lead to better vaccines and drugs to treat flu, the researchers report in the journal Cell Reports -- although any real-life applications of their work would be years away.

The Centers for Disease Control and Prevention reported on Friday that flu is widespread across 48 states and it’s hitting the elderly especially hard.

There’s a vaccine, but it’s not 100 percent effective and people have to get a fresh immunization every year. Two drugs -- Tamiflu and Relenza -- can help relieve symptoms but they’re not even close to being a cure.

But there may be a new way to shut the virus down. Benjamin tenOever and colleagues at the Mount Sinai school of medicine in New York found a way to trick the virus into leaving the safety of the cells it infects, making it vulnerable to the body’s immune system.

Like most viruses, flu hijacks healthy cells and forces them to turn out copy after copy of the virus. It has a type of internal clock to help it decide how long to stay. In the case of influenza, this is about eight hours, tenOever says.

If it works too slowly, the immune system can catch up to it. If it goes too fast, the virus dumps out of the cell it is infecting before it has time to multiply and spread itself. The researchers were able to engineer both types.

“This ‘viral clock signal’ has been disregarded previously, but it is actually an important drug target,” tenOever said in a statement. “We can make a drug that binds to this signaling factor, which would artificially make the virus tell time too slowly, so it sticks around in the cell for too long and gives the immune system plenty of time to respond.”

The findings could also be used to make a vaccine. The most effective vaccines use “live” viruses to prime a full immune defense, but it can be tricky to make one that doesn’t also make some people sick. One of the vaccines being used now, a nasal spray called FluMist, uses a live vaccine and it’s highly effective, but not recommended for use in people with weakened immune systems.

The clock mechanism might provide a way to make a flu vaccine that looks just like a normal flu virus to the immune system, but that is too incompetent to cause a real infection.

“If the spray vaccine were instead to deliver a virus that already had a defective ‘clock,’ even the compromised immune systems of the very young or very elderly would still have enough time to respond and destroy the virus before it would cause symptoms of an infection,” tenOever said.